A read/write head of a magnetic storage device such as a computer hard disk is positioned closely adjacent to the recording medium, separated from the recording medium by an air bearing that does not allow them to touch. A data bit is written onto an area, usually a track, of the recording medium using the writing portion of the read/write head by locally changing its magnetic state. That magnetic state is later sensed by the magnetoresistance sensor of the read/write head to read the data bit. Read/write heads are known in the art, and typical read/write heads are described, for example, in U.S. Pat. Nos. 3,908,194 and 6,043,960, whose disclosures are incorporated by reference.
The write portion of the read/write head typically includes an electromagnet with a pair of pole pieces. The pole pieces are projections that extend essentially perpendicular to the surface of a substrate to a height above the substrate of at least several times the width of the pole pieces. The width of the pole pieces approximates the width of the track in the recording medium. The narrower the track, the narrower are the pole pieces. A continuing objective in the development of such magnetic storage devices is to increase the areal density of information stored. One way to achieve this goal is to reduce the width of the recording tracks on the magnetic storage medium. To reduce the width of the recording tracks, the width of the pole pieces of the write portion of the read/write head must be correspondingly reduced.
A number of techniques are known for fabricating the pole pieces of the write head. These approaches require that the pole pieces be defined by photolithographic techniques at a dimensional scale comparable with the scale of the pole piece itself. The available lithographic techniques are satisfactory and operable when the pole pieces have width dimensions on the order of 1 micrometer. However, as the width dimensions are reduced to the order of ½ micrometer or less, the spatial resolution available with conventional photolithographic techniques becomes inadequate to define the pole pieces.
There is a need for an approach to fabricating a structure in the form of a projection extending above a substrate to a height of at least several times the width of the projection, where the width of the projection is very small. The present invention fulfills this need, and further provides related advantages.